Dependency of Crosstalk on Upper and Lower Cutoff Frequencies in PAM Time-Multiplexed Transmission Paths

In PAM time-multiplexed transmission systems, interchsnnel crosstalk arises when each sample is not confined to its assigned time slot. Even though perfect circuits are used to gather ideally-time-separated samples, subsequent transmission through a common medium of limited bandwidth causes each sample pulse to tail off into neighboring time slots, rather than be confined to its own time slot. Not only insufficient high-frequency transmission, but also insufficient low-frequency transmission can contribute significantly to inter-slot (hence interchannel) crosstalk when baseband signals are considered. In this paper, general crosstalk considerations in PAM timemultiplexed transmission paths are first discussed. The detailed dependency of crosstalk on upper and lower cutoff frequencies is then analyzed, considering all significantly-interfering samples. Some of the more formidable expressions that obtain are next reduced to very simple design equations by judicious application of valid and practical assumptions. The paper concludes with a numerical example and a few general comments concerning extensions and restrictions of the results. Major emphasis is placed on the lower cutoff dependency which has apparently received only empirical, not analytical, treatment in past literature.